Government workers

Union membership had declined dramatically in the private sector over the last 30 years, but not in government.

Workers at all levels of the public sector -- state, local and federal -- are heavily unionized. About 37% were union members in 2011. That's the same as in 1983, when the Department of Labor started tracking government union membership.

At the local level, these workers make a median of $973 a week, roughly $230 more than their non-union counterparts. They include millions of public sector teachers, police officers and firefighters, in addition to local administrators and bureaucrats.

The pay gap is slightly narrower for state workers. Federal workers, in contrast, earn about $54 less per week than their non-union colleagues.

Major unions: American Federation of State, County and Municipal Employees; Service Employees International Union; and American Federation of Government Employees